Conjecture on the asymptotic second eigenvalue of the Schoenberg operator

Let γΔn,k\gamma_{\Delta_n,k} denote the second largest eigenvalue of the Schoenberg operator associated with the fixed grid Δn\Delta_n and spline degree kk.

Schoenberg eigenvalue conjecture. For fixed k>0k>0,

γΔn,k1as n.\gamma_{\Delta_n,k}\to 1\quad\text{as }n\to\infty.

For fixed n>0n>0,

γΔn,k1as k.\gamma_{\Delta_n,k}\to 1\quad\text{as }k\to\infty.

The conjecture concerns whether the second largest eigenvalue can affect the convergence rate in the lower approximation bound. The source states that the eigenvalues and eigenfunctions of the Schoenberg operator are otherwise unknown and provides no resolution.

Sources & referencesView supporting material

Primary source

Johannes Nagler, Paula Cerejeiras and Brigitte Forster, “Lower bounds for the approximation with variation-diminishing splines”, arXiv:1402.2403 (2014).

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